1. Field of the Invention
The present invention relates to a receiving apparatus and a method for controlling the same.
2. Description of the Related Art
Due to advancements in liquid crystal panel manufacturing techniques in recent years, progress has been made towards a higher definition display screen for a television receiver. Along with this progress, the size of video data and audio data transmitted from an external apparatus, such as an HDD recorder, to a television receiver is increasing as well. In order to transmit large size data, an interface called an HDMI (High Definition Multimedia Interface) is often used (High-Definition Multimedia Interface Specification Version 1.3a). Television receivers equipped with a plurality of HDMI ports are also becoming widely used. HDMI is advantageous in that a complicated task of connecting a plurality of cables is eliminated because HDMI allows the transmission of video data and audio data with a single cable.
HDMI has a communication line called a CEC (Consumer Electronics Control) line. With the CEC, a receiving apparatus (e.g., a television receiver) and a transmitting apparatus (e.g., an HDD recorder) can be operated in conjunction with each other. For example, the receiving apparatus, when triggered by the power being turned off, transmits a Standby command to the transmitting apparatus, as a result of which, the power of the transmitting apparatus can be turned off as well. Likewise, the transmitting apparatus, when triggered by the start of playback, transmits an ImageViewOn command or TextViewOn command to the receiving apparatus, as a result of which, the power of the receiving apparatus is turned on. Then, the transmitting apparatus transmits an ActiveSource command to the receiving apparatus, and the receiving apparatus switches to an HDMI port serving as a data input source in accordance with the physical address stored in the command.
Such CEC communication becomes possible after the transmitting apparatus has obtained a physical address and a logical address. The transmitting apparatus obtains a physical address by reading an EDID (Extended Display Identification Data) ROM of the receiving apparatus by means of a DDC (Display Data Channel) line when an HPD (Hot Plug Detect) line of the receiving apparatus is enabled. Also, the transmitting apparatus obtains a logical address by sending a request to a logical address that the transmitting apparatus wants to obtain with a CEC command, and thereby confirming that the logical address is not in use.
However, some transmitting apparatuses cannot obtain a physical address and a logical address until after HDCP (High-bandwidth Digital Content Protection) authentication using a DDC line is completed after the EDID reading process ends.
On the other hand, the receiving apparatus, even when including a plurality of HDMI ports, generally performs HDCP authentication only with the apparatus that is connected to the HDMI port selected by the user. Consequently, the receiving apparatus enables only the HPD line of the port with which HDCP authentication is performed with the transmitting apparatus. Accordingly, if the transmitting apparatus clears the physical address and the logical address each time an HPD line is disabled, it cannot perform CEC communication.
Under the circumstances, Japanese Patent Laid-Open No. 2007-202115 discloses a technique for continuing CEC communication regardless of whether or not an HPD line is enabled. According to Japanese Patent Laid-Open No. 2007-202115, even when an HPD line is disabled, the transmitting apparatus continues CEC communication by using a physical address and a logical address that the transmitting apparatus has previously obtained and stored.
However, according to Japanese Patent Laid-Open No. 2007-202115, if the transmitting apparatus is connected, by the user, to an HDMI port whose HPD line is disabled or with which HDCP authentication is not possible, the transmitting apparatus continuously stores the previously obtained physical address and logical address. When the user then presses a playback button of the transmitting apparatus, the receiving apparatus cannot switch to the correct port that serves as a data input source because the physical address included in the ActiveSource command is a previously obtained value (that is, a value that does not correctly reflect the current connection status).